The NES (nonlinear energy sink) is a new type of nonlinear tuned mass damper that is connected to the shock-absorbing main structure through strong nonlinear stiffness and viscous damping. The vibrational energy in the main structure is transferred to the NES oscillator by means of target energy transfer. A shaking table test of a 1:4 scaled RC (Reinforced Concrete) frame structure model with a new type of NES shock absorber was conducted to study the damping effect of the NES shock absorber, especially for the influence of joint strength and deformation. The NES used in this experiment has a relatively large nonlinear stiffness and a wide vibration absorption frequency band. The variation of reinforcement strains, node failure mode, and structural natural frequency of 1 story and two-layer joints of the model frame structure with NES were studied. The test results showed that NES could effectively reduce the strains of longitudinal reinforcement and stirrup in beams and columns and delay the plastic hinge development at the bottom and the top of the column. The frame model with NES installed has failures at the beam ends and shear failures at the nodes, realizing the seismic mechanism of solid columns and weak beams. Compared with ordinary seismic structures, the NES can effectively reduce the shear stress of concrete at the joints and alleviate the shear failure of joints. The final failure of the NES shock absorbing structure was the yielding of the steel bars at the bottom of the column and the crushing of the concrete at the foot of the column, and the connection between the column foot and the backplane became loose simultaneously. The decreasing rate of the vibration frequency declined due to the NES with varied broadband absorbing capability. It can be seen that the NES shock absorber not only has a good effect on reducing the seismic response of the structure, but more importantly, the damage of the structural nodes is greatly reduced, and therefore, the seismic capacity of the structure improved.

This paper proposes a new type of composite box beam combined with cold-formed thin-walled steel and glued laminated timber to develop green building structures while improving the load-carrying capacity of a single steel girder and glued timber girder. Two composite beams composed of laminated timber and Q235 cold-formed thin-walled steel were designed and fabricated. Then, the shear performance test with quadratic loading was carried out to analyze the load carrying capacity, damage modes, and deformation characteristics of the test beams, as well as their influencing factors. Subsequently, a finite element model of the composite beam was established, and the loading mode was the same as that of the test to further study the parameters affecting the shear performance of the composite beam. The results of the study indicate that steel and glued timber in composite beams connected by adhesive bonding can work and deform together under load and each give full play to its material properties, especially the composite beams, which exhibit higher shear strength than a steel or timber beam. The effects of parameters such as steel cross-sectional area, shear span ratio, steel skeleton form, and steel cross-sectional strength on the shear capacity of the composite beams were observed, among which the shear span ratio had the greatest effect on the shear capacity of the composite beams. The shear capacity decreased by 14.3% and 19.5% when the shear span ratio was increased from 1.5 to 2.0 and 2.5, respectively. The shear capacity of the combined composite beams increased by 10.6%, 6.3%, and 5.8% when the thickness was increased from 1.5 mm to 2.0 mm, 2.5 mm, and 3.0 mm, respectively. When the combination of the steel cross-section was a box beam, the overall shear-bearing capacity could be increased by 12% compared with the “I” type composite beam, although its shear stiffness was close to that of the “I” section composite beam.

In order to mitigate the vibration caused by fluid–structure interaction in water-conveying pipelines, a semi-active control method based on a magnetorheological (MR) damper is proposed. First, the partial differential equation governing the pipeline micro-element, which is simply supported at both ends, is formulated. This equation is then transformed into state-space expressions through non-dimensionalization and the Galerkin method. Based on passive dissipative control theory, a semi-active control law ensuring Lyapunov global asymptotic stability is derived based on the relative motion between the dynamic vibration-absorbing mass and the pipeline. Next, an on–off control algorithm is designed for the MR damper. The results of simulation and hardware-in-loop experiments demonstrate that the semi-active control law can significantly reduce the vibration of the pipeline system. The contribution of this research is to propose a new MR tuned mass damper (MR-TMD) to suppress vibration in water-conveying pipelines. The proposed MR-TMD scheme and its control method provide a theoretical basis and practical reference for the engineering application of semi-active vibration control in water-conveying pipelines.

Based on an engineering project, this paper initially establishes an observation point for foundation pit and then determines monitor warning value. During project construction, we carried out an experiment on the horizontal movement and settlement and inclination of adjacent buildings and promptly monitored the foundation pit., Scientific analysis of the data is presented. This work is designed to provide for effective measures to implement security alerts for foundation construction.. Detailed analysis examines the causes of deformation of foundation pit and offers a reasonable treatment measure. Results offer some scientific basis and technical measures to guarantee deep foundation project construction security and more knowledgeable engineering construction. With the rapid development of urbanization in China, the deep excavation works requirehave been put forward strict demand regulations concerningdue to the requirements of the spatial location, structural stability and using function. Deep excavation engineering is mostly carried out in areas of heavy traffic and dense construction. The complexity associated with deep excavation depth and difficult construction creates environments where serious accidents can occur. The deep excavation work is a wide-ranging and integrated engineering process. Previous research on accidents in national deep foundation pit engineering found the general accident ratio was about 20% of that of the deep excavations work (Tang, 1997),. Most accidents in urban areas were caused by foundation pit support. In deep excavation engineering, both the strength and deformation of the supporting structure and the surrounding environment affected by pit deformation should be considered (Sun, 2006). The pit support systems are always temporary facilities with fewer safety considerations and more hazards. Working status and conditions are more complicated and uncertain. Thus, during the construction process, dynamic monitoring and control is very important. The content of deep excavation-site monitoring generally includes the horizontal displacement of supporting structure, tilt displacement of neighboring buildings, sedimentation of adjacent roads and so on. A monitoring crew should provide timely feedback information (Liu, 2006) to detect any problems and provide early warnings for reducing disasters. A monitoring program that provides critical information and manages deep excavation construction scientifically and effectively is the key to successful deep excavation construction (Liu et al., 2007).

To identify the location of the strongest vibration of skeletal membrane structures under pulsating wind and predict the response and damage of the structures. To guide engineering reinforcement, base on the platform of ANSYS Workbench as a platform, the complex skeleton membrane structure is first simplified using the modal fitting method, and the error of the 30th-order frequency of the membrane structure before and after the simplification is calculated to be less than 5% compared to the unsimplified model. Based on the simplified model, the unidirectional coupling and bidirectional coupling methods were compared using the surface averaging wind pressure distribution parameters of the membrane structure. The results show that the extreme value and extreme difference of the averaged wind pressure of the bidirectional coupling are larger than those of the unidirectional coupling under the same wind angle, which verifies the reliability of the vibration analysis of the large-span membrane structure under the bidirectional coupling. By analyzing the wind pressure coefficients at the key measure points, it can be seen that the structure is in unfavorable working condition at the wind angle of 0°–45°. Based on the bidirectional coupling method, the maximum displacement time variation curve, maximum acceleration time variation curve, and maximum equivalent force time variation curve for different wind direction angles are basically the same, and the membrane structure gradually equilibrates with time, and the maximum instantaneous displacement, maximum instantaneous acceleration, and maximum equivalent force all reach the maximum at wind direction angle 30° and the minimum at 90°.

In engineering practice, longitudinal brace systems for column-braced systems are designed to resist both horizontal and vertical loads. In previous experimental research on horizontal brace forces for column-braced systems of intermediate height, only vertical loads were considered. Hence, this paper presents a numerical simulation of numerous column-braced systems subjected to horizontal and vertical loads. In the numerical simulation, second-order analysis was adopted, and the Monte Carlo method was used to incorporate the randomness of initial imperfections in the horizontal brace and column. From the finite element (FE) analyses and probability model statistics, the normal probability density equation for intermediate-height horizontal brace forces under horizontal and vertical loads was obtained, and the corresponding design intermediate-height horizontal brace forces were determined and compared with those under vertical loads only. The results indicate that the design intermediate-height horizontal brace forces under horizontal and vertical loads are significantly greater than those under only vertical loads, and that the design intermediate-height horizontal brace forces under horizontal and vertical loads are also greater than the simple superposition results of horizontal loads and intermediate-height horizontal brace forces under only vertical loads.